1. Field of the Invention
The invention concerns filling an analysis card with a liquid medium.
2. State of the Art
xe2x80x9cAnalysis cardxe2x80x9d is to be understood as any means, which may or may not be disposable, with which it is possible to perform one or more analyses simultaneously using a single sample and one or more reagents, and to do this in a way that is sealed off from the external environment, the result of the analysis or analyses being obtained optically, for example. Such an analysis card generally comprises a body in which there is formed at least one reading cavity which, during use, receives all or part of the sample and has at least one reagent already present in said cavity, and an orifice communicating with said cavity via at least one internal channel. Said cavity or cavities thus communicate(s) with the outside only via the aforementioned orifice, whilst the card is generally joined to or cooperates with a flexible, external conduit communicating in a leaktight manner with this orifice. It is through this external conduit that it is possible to admit, in the manner described hereinafter, a sample of the liquid medium which is to be analyzed.
Such cards are well known in the prior art and in particular in U.S. Pat. Nos. 3,963,355 and 4,038,151, to which reference will be made as and when necessary.
xe2x80x9cLiquid mediumxe2x80x9d is to be understood as any substance or body which is liquid, at any rate capable of flowing by means of pumping, irrespective of the viscosity or fluidity of this liquid; in particular, where a biological analysis is concerned, the term liquid medium is to be understood as a medium which includes, for example, one or more microorganisms or a biological substance to be analyzed.
As regards the filling of an analysis card as defined above, the procedure to date has been as follows:
xe2x80x94use is made of a sealed chamber, with means for controlling the internal pressure, and in particular the vacuum when said chamber has been depressurized;
xe2x80x94on the one hand, a receptacle, for example a test tube, holding the liquid medium to be sampled or removed, is placed in the chamber, and, on the other hand, alongside the receptacle, the analysis card with the free end of the external conduit immersed in the liquid medium contained by the receptacle;
xe2x80x94the air is evacuated from the chamber until a significant vacuum has been created, for example below 100 mbar absolute, by which means the air is evacuated from the analysis card and the evacuated air passes through the liquid medium in the receptacle;
xe2x80x94after ending the vacuum, and returning the chamber to atmospheric pressure, the liquid medium is aspirated into the analysis card as far as the reading cavity or cavities, which are thus filled.
Such a procedure appears to be particularly contaminating, since the bubbling which occurs as the vacuum is established is capable of projecting particles or droplets of the liquid medium out of the receptacle and thus subsequently into contact with the user or operator, and this despite all the precautions that can be taken in this regard. In the case of a liquid medium containing a pathogenic agent, this seems to be unsatisfactory.
The subject of the present invention is a method for filling an analysis card in a non-contaminating manner since it proceeds at all times under negative pressure, that is to say without any possibility of the liquid medium used being evacuated to the outside.
According to the present invention, the following steps are carried out in succession:
xe2x80x94to evacuate the gas contained in the analysis card, the free end of the open external conduit is connected in a leaktight manner directly to an evacuation means outside the liquid medium used;
xe2x80x94the external conduit is closed in order to maintain the negative pressure in the analysis card;
xe2x80x94the free end of the closed external conduit is immersed in the liquid medium;
xe2x80x94and the external conduit is re-opened, after immersion of this free end, in order to aspirate the liquid medium into the analysis card.
The present invention also affords the crucial advantage that pumping the gas contained in the analysis card requires limited work and is consequently compatible with relatively simple, even rudimentary, pumping means, in particular manual ones. Moreover, the filling procedure described above can be used both manually as well as in the context of an automatic analysis.